In the first chapter of his fascinating book The Origins of Psychic Phenomena (1984), the British psychologist Stan Gooch explains that he used to smile when he heard, “for instance, stories of invisible ‘thought forms’ allegedly produced by Tibetan mystics and others.” He then adds: “I no longer smile at such stories. My own feeling, now, is that there may literally be no limit to what can be achieved by the human subjective mind manipulating and actualising itself in the external, objective universe around it.”

According to Gooch, the workings of the unconscious mind – or subjective mind – can shed light on a whole host of paranormal phenomena, including poltergeist disturbances, mediumship, automatic writing, multiple-personality-disorder, succubi and incubi attacks, and even UFO sightings. The list goes on.